An iAVs Case Study

This is an excerpt from the iAVs Handbook

The commercial-scale project established by Dr. Boone Mora, a retired veterinarian and self-described “jack-of-all-trades” (McClintic, 1994), in Bath, North Carolina, serves as a key example of the feasibility and profitability of iAVs. After attending an iAVs workshop taught by Dr. Mark McMurtry, Dr. Mora became a proponent of the technology, believing it held “real possibilities and great potential” (Mora, 1994). Mora saw his role clearly: “A North Carolina State University student named Mark McMurtry came up with the idea… Then we came in and scaled up their research to a commercial-size operation” (McClintic, 1994).

In 1993, he successfully secured a grant from the five-county Mid-east Resource Conservation and Development Council, coordinated by Tim Garrett. This case study outlines the project’s remarkable successes, which were achieved with the support of the council and NCSU.

During the two-year demonstration project, Mora’s main crops were tomatoes, European cucumbers, and European peppers. He also experimented with okra, baby cucumbers, and passion fruit (McClintic 1994).

When I say we, I refer primarily to Tim Garrett–the coordinator for the five-county Mid-east Resource Conservation and Development Council and myself.  Tim shared the joy of building the structure and helped with operation where possible and necessary.  My wife Jean also helped a great deal. First let us expose our limits.  We do not claim any originality to the idea.   Mark McMurtry, while a graduate student at North Carolina State University had the stamina and tenacity, and an advisor with foresight in Dr. Doug Saunders, to push through the opportunity to do his doctoral dissertation on the subject. The subject did not fit snugly into horticulture, for you do not do aquaculture in horticulture normally.  Nor did it conform narrowly to aquaculture for you do not do horticulture in aquaculture.  Try persuading one discipline or the other to take you on and the “other” looms big and out of sync.  Dr. McMurtry persisted and was successful however and is to be commended.  We consider him the international expert on the subject.”

– Boone Mora

In his own account, Dr. Mora is quick to credit the originator of the technology, stating, “We do not claim any originality to the idea” (Mora, 1994). He credits Dr. Mark McMurtry, whom he calls the “international expert on the subject,” for his persistence as a graduate student at North Carolina State University. Mora notes that McMurtry’s advisor, Dr. Doug Saunders, showed great foresight in supporting the research, as the topic “did not fit snugly into horticulture… Nor did it conform narrowly to aquiculture” (Mora, 1994). This interdisciplinary challenge highlights the novelty of the iAVs concept at the time.

Dr. McMurtry was in Africa during its implementation. The system was managed by Dr. Mora, his wife Jean, and Tim Garrett, with occasional local labor. Mora (1994) noted that his wife “helped a great deal” and that Garrett “helped with operation where possible and necessary.”

The project was conducted from 1992 to 1994 on the site of an NCSU Horticultural Research Station near Greenville, NC, where a defunct greenhouse was re-erected for the operation (McClintic, 1994; Mora, 1994). The primary objective was to demonstrate a viable alternative income source for farmers by implementing Dr. McMurtry’s iAVs research on a commercial scale.

The system was operated under challenging conditions, with no water temperature regulation, no CO2​ augmentation, no evaporative cooling system, and marginal aeration. Remarkably, despite these limitations, the project thrived without the use of any pesticides. As Mora explained, “What’s neat about this kind of system is that everything is produced organically. The fish wastes are a great source of fertilizer for vegetables” (McClintic, 1994).

The construction was a significant, hands-on undertaking. Dr. Mora (1994) noted they had “no money for builders” and consequently spent about 10 months building the greenhouse themselves. The facility was a 100 x 100-foot, 3-bay gutter-connected greenhouse. 

Dr. Mora (1994) specified that they adapted these dimensions by modifying “the plans for a 34 x 300 foot tobacco plant greenhouse by Williamson.” The greenhouse featured two 26,000-gallon fish tanks lined with plastic. The fish tanks were built by digging pits with V-bottoms.(McClintic 1994).

“Tanks were dug with excavators. Our tanks were 10 feet wide and approximately 90 feet long and went straight down for 3 feet and then sloped to the middle where the water was about 5 feet deep. The tank walls extended about 6 inches above the water. I do not recommend this shape of tank. It is difficult to dig and the sides cave in when water in the tank is low or empty. Perhaps it would be well to slope the sides about 20-25 degrees instead of going straight down.”

“In our part of the country, (coastal North Carolina), most of the sand is a fine texture and we had to import builders sand the best we could but we never felt like it was as coarse as we would have liked. Sand is only as coarse as the fine particles in the mixture because the fine particles will plug up the space between the large particles and retard water flow.”

The top of the sand bed was leveled by hand. A good way to do this is to stop-up the drains, flood the bed with water up to the approximate level of the sand. Then using a drag made of 2x4s, make the frame approximately 2’x 8′ and attach a rope for pulling, add a cross piece of plywood or something to set a plastic bucket on with sand in it for weight. The high spots in the beds can be dragged into the low spots using the level water surface as a guide. Walls around the sand should be at least a few inches (4-6) higher than the sand (more if you like).

“Alongside the fish tanks, we grew vegetables in sand beds. Every hour during daylight, pumps automatically removed water containing feed and fish wastes from the bottom of the tanks. The water was delivered to the beds and used to irrigate the vegetables.” With a 10-20 minute flood and 40-50 minute drain cycle (Mora, 1994).

The nutrient-rich water was filtered as it seeped through the sand beds. The sand was inoculated with bacteria that
convert ammonia to nitrates, which can be used by plants. The filtered water went into a series of drainage lines that delivered it back to the fish tanks (McClintic 1994).

“Once a week, I topped off the fish tanks with fresh water,” Mora says. “What’s neat about this kind of system is that everything is produced organically. The fish wastes are a great source of fertilizer for vegetables” (McClintic 1994).

“A network of perforated 4” corrugated plastic drain tile lay on the bottom in the sand – the corrugated perforated plastic pipes for collecting and draining the water are placed every 8 feet so that they collect water from 4 feet on each side. So put your first pipe 4 feet from the first wall and then 8 feet apart thereafter until you get within 4 feet of the last wall. Cover the tile with a fine nylon cloth, used by drain contractors, to keep the sand out of the pipe.

We purchased the concentrated preparation of bacteria and used about l/4 or less of the recommended amount. They will multiply in the bed and do a good job.

“We stocked the tanks with male hybrid tilapia, which are hardy, fast-growing fish,” Mora stated (McClintic, 1994).

Fish fry or fingerlings were added monthly, with marketable fish (1.25-1.50 lbs.) harvested after six to seven months. The tanks were divided into seven compartments to separate fish by size for continuous harvesting without moving large numbers of fish.

“One of the faster growing fish (Tilapia) is the hybrid of the Aureus and Nilotica strains of Tilapia. It is best to stock all males or sex reversed or sex neutered or sex separated. Females do not grow fast because their energy goes
into producing young instead of muscle. To “sex reverse” tilapia, newly hatched fry are exposed to testosterone for a short time and that changes their ability to form eggs. We bought fry already reversed.”

“We have sold them in sizes from a quarter pound on up. We sold them live to dealers that come 500 miles with
tanks and oxygen to pick up 500-2,000 pounds; we sold them super chilled and packed in ice and sold them filleted. Selling them live at the greenhouse in bulk is preferred for it is less work, less expense, and a higher price.”

During its first year of operation, the project yielded impressive production metrics, which were comparable or slightly improved in the second year. The USDA-funded trial reported significant yields:

• Fish Production: The system produced sex-reversed Nile Tilapia (Oreochromis niloticus) with a biomass increase of 113.5 kg/m3/yr.

Vegetable Production

• Cucumber: 25 to 30 kg/m2 per crop
• Peppers: 15 to 20 kg/m2 per crop
• Tomatoes: 20 to 25 kg/m2 per crop
• Lettuce: Successfully grown as an intercrop in rotation, though yields were not formally measured.
• Feed Conversion Ratio (FCR): An excellent FCR ranging from 1:1.25 to 1:1.30 was achieved.

Beyond the measured yields, Mora estimated the system’s full potential. He believed that with good management, the quarter-acre greenhouse could produce “around 100,000 pounds of vegetables and 50,000 pounds of fish a year” (McClintic, 1994).

Mora estimated that a producer using their own labor “could build and equip this size greenhouse for about $40,000” (McClintic, 1994). Despite significant market challenges—including local unfamiliarity with tilapia and having to sell produce at low unit prices—the project was highly profitable. After covering all operational expenses and paying a living salary, Dr. Mora generated a significant annual profit. Reports from the NCRDC place this profit in the range of $30,000 to $40,000 per year, a figure corroborated by Mora’s own estimate that a producer could “easily be able to net $25,000 to $30,000 a year” (McClintic, 1994).

Despite this significant market challenge, the project was highly profitable. After covering all operational expenses and paying a living salary to himself and his staff, Dr. Mora generated a significant annual profit. Reports from the North Carolina Resource Conservation and Development Council (NCRDC) place this profit in the range of $30,000 to $40,000 per year. Another account specifies a profit of approximately $50,000 annually (equivalent to over $78,500 in 2011 dollars). This achievement firmly demonstrated that iAVs could be a robust and economically viable enterprise even with minimal environmental controls and in a challenging market. The operation ceased only because Dr. Mora’s advancing age and declining health prevented him from continuing the daily work, not due to any technical or financial failure.

Subsequent analysis highlights the system’s even greater economic potential under different market conditions. One estimate calculated a potential wholesale value of $325,000 per year (based on 2016 pricing). Furthermore, projections based on ideal production ratios (v:v 1:2+, v:a 1:6+, feed-fish:fruit 1:7+) suggest the system could support:

A primary challenge was what Dr. Mora (1994) called a key “mistake” in their initial setup: the sand. He explained, “We first used sand that incidentally had mollusk shell and phosphate nodules in it… the pH of the water stayed between 8.3 and 8.5.” To correct this, the team undertook a major overhaul. Mora (1994) detailed the solution: “we added walls to the sand beds, put down a new piece of 6 mil. plastic liner, new drain pipe network, and a new and different sand.” This comprehensive replacement successfully resolved the pH issue.

Disease management was another issue – particularly southern tomato wilt. “We never solved that problem but feel that it probably can be solved by sterilizing the sand (before inoculating with nitrifying bacteria) and maintaining a strict practice of good sanitation which includes showers and greenhouse clothes, boots, and foot baths before entering the sand beds. As I think about it, well-water (deep or shallow) might be a source of the southern
tomato wilt bacteria and by first chlorinating and then aerating or dechlorinating the water before or in the process of filling the fish tank might be a possibility that is within the economic and technological reach of a commercial system.”

“Like sanitation if you are not going to do the maximum to control plant pests then you might ought to forget it. Excellent sanitation and good circulation of air is probably the most important controlling factor in this and other potential diseases.”

The project was viewed by its founders as a critical learning experience. Dr. Mora (1994) expressed a desire for further funding “to put into practice the critical things we think we learned,” framing the project’s value in its ability to inform future efforts. He stated, “We hope you can be persuaded not to make some of the mistakes we made which is only one of the sides of the research coin.” This philosophy underpins the following recommendations:

Mora strongly recommended starting small, advising that a producer “might be wise to begin with a smaller 30×50-foot or 30×100-foot greenhouse until he or she works all the bugs out of the system,” noting that “it’s easy to expand later” (McClintic, 1994). He emphasized using coarse sand inoculated with nitrifying bacteria and maintaining a proper slope in the sand beds for effective drainage. Reflecting on his own experience, Mora (1994) noted that their sand “was not as coarse as I think it should have been,” which directly impacted the efficiency of the drain cycle.

“I wholesaled the fish and vegetables to-supermarkets in my area for about $1 a pound,” Mora says.

“Whatever system you use for aeration, you will want a back up in case of mechanical or electronic failure. Some air pumps, after about three years, will not resume operating once it is turned off.”

“We used a 3-bay gutter connected quarter acre greenhouse. We modified the plans for a 34 x 300 foot tobacco plant greenhouse by Williamson. We made it into a l00′ x 100′ greenhouse. We made steel trusses and installed them every l0 feet. Except for the trusses, the remainder of the house is salt treated preserved wood and was assembled with screws. Rim shanked nails would probably work as well and easier to use. The bays were connected with gutters we made from salt-treated wood and rolled aluminum. The inflated walls and roof
were double layers of plastic which were anchored in an interlocking aluminum clip that came in 8-foot pieces. Small inflation fans were installed as needed to keep the plastic inflated.”

“We had the two fish tanks (26,000 gallons each) in the middle bay. Many other varieties of greenhouse design might work as well or better. Perhaps of great importance is the need for the sides to be high enough for the
plants to grow up to 7 feet tall or as high as you can reach. For a quonset type greenhouse, the legs could be anchored to posts that are 5-7 feet high giving a height of 8 feet or so at the side. I would encourage you to
use your own ingenuity for “arranging” things in the greenhouse and choosing building methods and designs and keep us informed of your successes, failures, questions, comments, and ideas that you are willing to share.”

The USDA-funded Commercial Trial confirmed iAVs commercial potential:

• Yield Comparison: Fish yield per cubic meter was 2.8 times UVI’s best result; plant yield was 9.3 times UVI’s mean best.
• Water Efficiency: iAVs used only 27% of system water capacity and 19% of annual water volume compared to the University of the Virgin Islands (UVI) system.
• Revenue Generation: iAVs generated 7.5 times more gross revenue per square meter (minus direct fish costs) than UVI.
• Equipment Costs: iAVs equipment costs were only 30% of UVI’s system, with annual revenue/equipment + material costs being 15.7 times higher.

This analysis highlights what an iAVs could achieve under ideal production ratios and favorable market conditions, adjusting to the suggested baseline ratios i.e., v:v (1:2+), v:a (1:6+), (feed-fish):fruit (1:7+)building upon the practical success demonstrated by Dr. Boone Mora’s project.

22.7k kg fish, (i.e.~30k kg feed, to Pmf 250g in <120 days 3x/yr or 350g <180 days 2x/yr)   – is enough TAN and excrement to grow 

• 8,000 to 10,000 indeterminate tomato plants (on 12 mo cycle)  (9,000 applied below)
  • (or 3 times that if a 4-month crop interval 3x/yr, and/or equivalent crops)

2016 estimated  US ‘organic’ bulk wholesale valuations:

• tilapia (live): 22.7k kg x $3.30/kg = $75k/yr 
• No. 1 ‘organic’ tomato: 170k kg x $5.5/kg = $935k/yr
• No. 2 ‘organic’ tomato: 40k kg x $3.5/kg = $140k/yr
• Total above (without intercrops etc) = $1,150k ($300/m2/yr)

At 2015 Philly Terminal wholesale prices. 

• Organic No 1 @ $6.90/kg -10% = $6.20/kg  (> $1,056k)
• Organic No 2 @ $4.80/kg – 10% = $4.35/kg  (> $174k)
• Total w/ fish $1,305k or $343/m2/yr)
•        w/ very hi-tech GH with intercrops from $450 to 500/m2/yr) 

• …   + 30-50% or more when retailed, direct-marketed, NTM value-added processing

This means that 22,700 kg (approximately 50,000 lbs) of fish, specifically tilapia, could be produced annually. This fish production is estimated to require around 30,000 kg of feed and could be achieved by growing fish to a marketable size of 250g in less than 120 days (three times a year) or 350g in less than 180 days (two times a year). 

This volume of fish production is projected to generate sufficient nitrogen (TAN) and excrement to support the growth of 8,000 to 10,000 indeterminate tomato plants. The projection specifically applies to 9,000 tomato plants on a 12-month cycle, or potentially three times that number if grown on a 4-month crop interval (three times a year), or equivalent crops.

With a “very hi-tech GH (greenhouse) with intercrops,” the value could rise to $450 to $500 per square meter per year. Additionally, if products are retailed, direct-marketed, or undergo “value-added processing,” the profit could increase by 30-50% or more.

While Dr. Mora’s initial project demonstrated profitability in a challenging market and with minimal environmental controls, generating annual profits of $30,000 to $50,000, these projections highlight a significantly higher revenue potential, underscoring the technology’s long-term viability and scalability.

2025 Update:

Tilapia (live, wholesale): A more realistic 2024/2025 bulk wholesale price is in the range of $5.00 – $6.00/kg. We will use a conservative estimate; 22,700 kg x $5.10/kg = $115,770 / yr

No. 1 ‘Organic’ Tomato (e.g., Greenhouse Tomatoes on the Vine): High-quality, certified organic, locally grown tomatoes command a strong premium. Current wholesale prices for contracted, high-volume organic greenhouse tomatoes are closer to $7.50 – $9.00/kg: 170,000 kg x $7.92/kg = $1,346,400 / yr

No. 2 ‘Organic’ Tomato: The price for No. 2 grade produce has also increased, maintaining a consistent discount relative to No. 1 grade: 40,000 kg x $5.40/kg = $216,000 / yr

Updated High-Tech Projection (2025): from $550 to $650 / m^2 / yr

Boone Mora’s iAVs demonstration project proved that integrated aquaculture and vegetable culture can be both environmentally sustainable and economically viable. Its success was not just in production, but in education and inspiration. 

Oh yeah, Tilapia can be caught easily on hook and line with canned or frozen corn kernels as bait.  Nothing like roughing it in a greenhouse!

– Boone Mora

“Actually we left out perhaps an important item. You will probably need two houses. One for work and one for show. Because once the word gets out every class within a hundred miles will want a tour–some several times. You will
get requests from far and wide–individuals and large groups. You will be novel, interesting, and exciting. Resist this and stay humble. At least keep them out of your “clean” greenhouse or you will never control diseases and pests again.

According to McClintic (1994), “Over 1,500 people have toured the demonstration greenhouse, and now some are starting their own enterprises.” The operation ceased only because Dr. Mora’s advancing age and declining health prevented him from continuing the daily work. The project’s legacy continued, however, as Mora confirmed that they “ended up selling the demonstration greenhouse to a vegetable grower” (McClintic, 1994), ensuring the facility remained in productive use. This transition underscores that the project’s end was a personal one, not a technical or financial failure, cementing its status as a landmark success in iAVs commercialization.

• McClintic, Dennis. 1994. Double-duty greenhouse. The Furrow. March-April. p. 41–42
• Boone Mora – Email 1994